DIAGNOSIS The built-in print head cleaning cycle often isn't aggressive enough if the nozzles have been clogged for a bit. The ink in the INKvestment tanks can sometimes get a little thick if not used regularly.
FIX Don't just run the cleaning utility over and over—it wastes ink. Go into your printer's settings menu on the LCD screen. Navigate to Maintenance > Print Head Cleaning. Run the 'Standard' cleaning once. Print a nozzle check pattern (also in the Maintenance menu). If it's still bad, run the 'Deep Cleaning' cycle. Wait an hour, then print another nozzle check. It often takes a few hours for the cleaning fluid to work.
IF THAT DIDN'T WORK If one color is completely missing or severely distorted, the issue might be with that specific INKvestment tank. Try removing it, checking the air vent (the little hole on top) isn't blocked, and re-seating it firmly. A faulty tank can fail to supply ink properly.
HEADS UP The deep cleaning cycle uses a significant amount of ink. If you're doing them back-to-back, you might drain a color tank faster than you expect, especially if the clog is severe.